KR20200014333A - Electrolyte Composition and Secondary Battery - Google Patents

Abstract

An electrolyte composition containing one or two or more polymers, oxide particles having a hydrophobic surface, at least one electrolyte salt selected from the group consisting of lithium salts, sodium salts, calcium salts and magnesium salts, and an ionic liquid Is initiated.

Description

Electrolyte Composition and Secondary Battery

The present invention relates to an electrolyte composition and a secondary battery.

BACKGROUND ART In recent years, high performance secondary batteries are required due to the widespread use of portable electronic devices and electric vehicles. Among them, lithium secondary batteries have high energy density, and thus, they are attracting attention as power sources for batteries for electric vehicles and batteries for electric power storage. Specifically, a lithium secondary battery as an electric vehicle battery is a zero emission electric vehicle without an engine, a hybrid electric vehicle equipped with both an engine and a secondary battery, a plug-in hybrid electric vehicle that is directly charged from an electric power system, and the like. It is adopted in the electric car of the. Moreover, the lithium secondary battery as an electric power storage battery is used for the stationary electric power storage system etc. which supply the electric power previously stored at the time of emergency by which the electric power system was interrupted | blocked.

In order to use for such a wide range of applications, higher energy density lithium secondary batteries are required and their development has been made. In particular, in the lithium secondary battery for electric vehicles, high safety is required in addition to high input / output characteristics and high energy density, and thus a higher level of technology for securing safety is required.

Conventionally, as a method of improving the safety of a lithium secondary battery, the method of flame retarding an electrolyte solution by addition of a flame retardant, the method of changing electrolyte solution into a polymer electrolyte or a gel electrolyte, etc. are known. In particular, since the gel electrolyte has an ionic conductivity equivalent to that of the electrolyte used in a conventional lithium secondary battery, the method of converting the electrolyte into a gel electrolyte does not deteriorate battery performance and reduces the amount of advantageous electrolyte so as to burn the electrolyte. Can be suppressed.

Patent document 1 is disclosing the gel electrolyte layer containing the plasticizer containing a lithium salt, the matrix polymer which disperse | distributes a plasticizer, and a fibrous insoluble matter. The fibrous insolubles contained in the gel electrolyte in an amount of 0.1 wt% or more and 50 wt% or less have a ratio of fiber length and fiber diameter of 10 or more and 3000 or less, fiber length of 10 or more and 1 cm or less, and fiber diameter of 0.05 or more and 50 or less By doing so, the cycle characteristics and the high temperature storage characteristics of the battery are improved.

Patent document 2 discloses a gel electrolyte and a gel electrolyte battery. The gel electrolyte layer is formed by swelling the matrix polymer with an electrolyte solution and contains a lot of low viscosity solvents having a low boiling point. By using a gel electrolyte containing a lot of low boiling point and low viscosity solvents, a gel electrolyte battery excellent in temperature characteristics, current characteristics, capacity, and charge / discharge characteristics at low temperatures is provided.

Japanese Patent Laid-Open No. 2000-164254 Japanese Patent Laid-Open No. 2007-141467

However, the conductivity of the conventional gel electrolyte as described above is insufficient, and when these are applied to the secondary battery as an electrolyte, for example, there is a fear that the discharge characteristics of the secondary battery will be significantly reduced.

Then, a main object of this invention is to provide the electrolyte composition which can manufacture the secondary battery which is excellent in discharge characteristics.

The first aspect of the present invention is at least one electrolyte salt selected from the group consisting of one or two or more polymers, oxide particles having a hydrophobic surface, lithium salts, sodium salts, calcium salts and magnesium salts, Electrolyte composition containing an ionic liquid.

The oxide particles are preferably surface treated with a silicon-containing compound. The silicon-containing compound is preferably at least one selected from the group consisting of alkoxysilanes, epoxy group-containing silanes, amino group-containing silanes, (meth) acryloyl group-containing silanes, silazanes, and siloxanes.

The oxide particles are preferably at least one particle selected from the group consisting of SiO ₂ , Al ₂ O ₃ , AlOOH, MgO, CaO, ZrO ₂ , TiO ₂ , Li ₇ La ₃ Zr ₂ O ₁₂ and BaTiO ₃ . .

The ionic liquid preferably contains at least one member selected from the group consisting of a linear quaternary onium cation, piperidinium cation, pyrrolidinium cation, pyridinium cation and imidazolium cation as a cation component.

The ionic liquid preferably contains at least one of the anionic components represented by the following general formula (A) as the anionic component.

N (SO ₂ C _m F _{2m + 1} ) (SO ₂ C _n F _{2n + 1} ) ^- (A)

[m and n each independently represent an integer of 0 to 5]

The polymer preferably has a first structural unit selected from the group consisting of ethylene tetrafluoride and vinylidene fluoride.

The polymer is preferably a second structural unit selected from the group consisting of the first structural unit and hexafluoropropylene, acrylic acid, maleic acid, ethyl methacrylate and methyl methacrylate in the structural unit constituting the polymer. Included.

The electrolyte salt is preferably an imide lithium salt.

A second aspect of the present invention is a secondary battery including a positive electrode, a negative electrode, and an electrolyte layer containing an electrolyte composition provided between the positive electrode and the negative electrode.

According to this invention, the electrolyte composition which can manufacture the secondary battery excellent in discharge characteristics can be provided. In addition, according to the present invention, a secondary battery using such an electrolyte composition can be provided.

1 is a perspective view illustrating a secondary battery according to a first embodiment.
FIG. 2 is an exploded perspective view showing an embodiment of an electrode group in the secondary battery illustrated in FIG. 1.
3 is a schematic cross-sectional view showing an embodiment of an electrode group in the secondary battery shown in FIG. 1.
4A is a schematic sectional view showing an electrolyte sheet according to one embodiment, and (b) is a schematic sectional view showing an electrolyte sheet according to another embodiment.
FIG. 5: is a schematic cross section which shows one Embodiment of the electrode group in the secondary battery which concerns on 2nd Embodiment.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described, referring drawings suitably. However, this invention is not limited to the following embodiment. In the following embodiments, its components (including steps and the like) are not essential except as specifically stated. The size of the component in each figure is conceptual, and the relative relationship of the size between components is not limited to what was shown in each figure.

The numerical value and its range in this specification do not limit this invention. In this specification, the numerical range shown using "-" shows the range which includes the numerical value described before and after "-" as minimum and maximum value, respectively. In the numerical range described step by step in this specification, the upper limit or the lower limit described in one numerical range may be replaced by the upper limit or the lower limit described in another stage. In addition, in the numerical range described in this specification, you may substitute the upper limit or the lower limit of the numerical range by the value shown in the Example.

[First Embodiment]

1 is a perspective view illustrating a secondary battery according to a first embodiment. As shown in FIG. 1, the secondary battery 1 includes an electrode group 2 composed of a positive electrode, a negative electrode, and an electrolyte layer, and a bag-shaped battery exterior body 3 accommodating the electrode group 2. have. The positive electrode current collector tab 4 and the negative electrode current collector tab 5 are provided in the positive electrode and the negative electrode, respectively. The positive electrode current collector tab 4 and the negative electrode current collector tab 5 protrude from the inside of the battery exterior body 3 to the outside so that the positive electrode and the negative electrode can be electrically connected to the outside of the secondary battery 1, respectively.

The battery exterior body 3 may be formed with a laminated film, for example. The laminate film may be a laminated film in which resin films such as polyethylene terephthalate (PET) film, metal foil such as aluminum, copper, stainless steel, and sealant layers such as polypropylene are laminated in this order.

FIG. 2 is an exploded perspective view showing an embodiment of the electrode group 2 in the secondary battery 1 shown in FIG. 1. FIG. 3: is a schematic cross section which shows one Embodiment of the electrode group 2 in the secondary battery 1 shown in FIG. As shown in FIG. 2 and FIG. 3, the electrode group 2A according to the present embodiment includes the positive electrode 6, the electrolyte layer 7, and the negative electrode 8 in this order. The positive electrode 6 includes a positive electrode current collector 9 and a positive electrode mixture layer 10 provided on the positive electrode current collector 9. The positive electrode current collector 9 is provided with a positive electrode current collector tab 4. The negative electrode 8 includes a negative electrode current collector 11 and a negative electrode mixture layer 12 provided on the negative electrode current collector 11. The negative electrode current collector 11 is provided with a negative electrode current collector tab 5.

The positive electrode current collector 9 may be made of aluminum, stainless steel, titanium, or the like. Specifically, the positive electrode current collector 9 may be, for example, a perforated foil made of aluminum having a hole having a hole diameter of 0.1 to 10 mm, an expanded metal, a foamed metal plate, or the like. In addition to the above, the positive electrode current collector 9 may be formed of any material as long as it does not cause changes in dissolution, oxidation, or the like during use of the battery, and its shape, manufacturing method, and the like are not limited.

The thickness of the positive electrode current collector 9 may be 10 μm or more and 100 μm or less, and from the viewpoint of reducing the volume of the entire positive electrode, preferably 10 μm or more and 50 μm or less, and winding the positive electrode with a small curvature when forming a battery. From a viewpoint to make it more preferable, they are 10 micrometers or more and 20 micrometers or less.

In one embodiment, the positive electrode mixture layer 10 contains a positive electrode active material, a conductive agent, and a binder.

The positive electrode active material may be a lithium transition metal compound such as a lithium transition metal oxide or a lithium transition metal phosphate.

The lithium transition metal oxide may be, for example, lithium manganate, lithium nickelate, lithium cobalt acid, or the like. Lithium transition metal oxide is a part of transition metals such as Mn, Ni, Co, and the like contained in lithium manganate, lithium nickelate, lithium cobalt, and the like, one or two or more other transition metals or metal elements such as Mg, Al ( Lithium transition metal oxide substituted with a typical element). That is, the lithium transition metal oxide may be a compound represented by LiM ¹ O ₂ or LiM ¹ O ₄ (M ¹ contains at least one kind of transition metal). Specifically, the lithium transition metal oxide may be Li (Co _1/3 Ni _1/3 Mn _1/3 ) O ₂ , LiNi _1/2 Mn _1/2 O ₂ , LiNi _1/2 Mn _3/2 O ₄ , or the like. .

The lithium transition metal oxide is preferably a compound represented by the following formula (1) from the viewpoint of further improving the energy density.

Li _a Ni _b Co _c M ² _d O _{2 + e} (1)

[In Formula (1), M <^2> is at least 1 sort (s) chosen from the group which consists of Al, Mn, Mg, and Ca, and a, b, c, d, and e are respectively 0.2 <= a <= 1.2, 0.5 <= b <0.9 , 0.1 ≦ c ≦ 0.4, 0 ≦ d ≦ 0.2, −0.2 ≦ e ≦ 0.2, and b + c + d = 1.]

Lithium transition metal phosphate is selected from the group consisting of LiFePO ₄ , LiMnPO ₄ , LiMn _x M ³ _1-x PO ₄ (0.3≤x≤1, M ³ is Fe, Ni, Co, Ti, Cu, Zn, Mg and Zr At least one element).

The positive electrode active material may be unassembled primary particles or granulated secondary particles.

The particle diameter of the positive electrode active material is adjusted to be equal to or less than the thickness of the positive electrode mixture layer 10. In the case where the coarse particles having the particle size of the positive electrode mixture layer 10 or more are included in the positive electrode active material, the coarse particles are removed in advance by sieve classification, air flow classification, or the like, and the positive electrode active material having the particle size of the thickness of the positive electrode mixture layer 10 or less. Screening.

Preferably the average particle diameter of a positive electrode active material is 0.1 micrometer or more, More preferably, it is 1 micrometer or more, Preferably it is 30 micrometers or less, More preferably, it is 25 micrometers or less. The average particle diameter of a positive electrode active material is particle diameter (D50) when the ratio (volume fraction) with respect to the volume of the whole positive electrode active material is 50%. The average particle diameter (D50) of the positive electrode active material is obtained by measuring a suspension in which the positive electrode active material is suspended in water by a laser scattering method using a laser scattering particle size measuring device (for example, a microtrack).

70 mass% or more, 80 mass% or more, or 85 mass% or more may be sufficient as content of a positive electrode active material based on the positive electrode mixture layer whole quantity. Content of a positive electrode active material may be 95 mass% or less, 92 mass% or less, or 90 mass% or less based on the positive electrode mixture layer whole quantity.

Although a conductive agent is not specifically limited, Carbon materials, such as graphite, acetylene black, carbon black, carbon fiber, and a carbon nanotube, may be sufficient. The conductive agent may be a mixture of two or more kinds of the carbon materials described above.

The content of the conductive agent may be 0.1% by mass or more, 1% by mass or more, or 3% by mass or more based on the total amount of the positive electrode mixture layer. The content of the conductive agent is preferably 15% by mass or less based on the total amount of the positive electrode mixture layer from the viewpoint of suppressing the increase in the volume of the positive electrode 6 and the decrease in the energy density of the secondary battery 1 accompanying it. More preferably, it is 10 mass% or less, More preferably, it is 8 mass% or less.

The binder is not limited as long as it does not decompose on the surface of the positive electrode 6, but in the group consisting of ethylene tetrafluoride, vinylidene fluoride, hexafluoropropylene, acrylic acid, maleic acid, ethyl methacrylate and methyl methacrylate The polymer containing at least 1 sort (s) selected as a monomer unit, rubber, such as styrene butadiene rubber, isoprene rubber, an acrylic rubber, etc. may be sufficient. The binder is preferably a copolymer containing ethylene tetrafluoride and vinylidene fluoride as structural units.

The content of the binder may be 0.5% by mass or more, 1% by mass or more, or 3% by mass or more based on the total amount of the positive electrode mixture layer. 20 mass% or less, 15 mass% or less, or 10 mass% or less may be sufficient as content of a binder based on the positive electrode mixture layer whole quantity.

The positive electrode mixture layer 10 may further contain an ionic liquid.

As the ionic liquid, an ionic liquid used in an electrolyte composition described later can be used. The content of the ionic liquid contained in the positive electrode mixture layer 10 is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, based on the total amount of the positive electrode mixture layer. to be. The content of the ionic liquid contained in the positive electrode mixture layer 10 is preferably 30% by mass or less, more preferably 25% by mass or less, even more preferably 20% by mass or less based on the total amount of the positive electrode mixture layer. to be.

The electrolyte salt may be dissolved in the ionic liquid contained in the positive electrode mixture layer 10. As the electrolyte salt, an electrolyte salt used in the electrolyte composition described later can be used.

The thickness of the positive mix layer 10 is a thickness more than the average particle diameter of a positive electrode active material from a viewpoint of further improving electrical conductivity, and it should just be 10 micrometers or more, 15 micrometers or more, or 20 micrometers or more specifically. The thickness of the positive mix layer 10 should just be 100 micrometers or less, 80 micrometers or less, or 70 micrometers or less. By setting the thickness of the positive electrode mixture layer to 100 μm or less, the bias of charge and discharge resulting from variations in the charge level of the positive electrode active material in the vicinity of the surface of the positive electrode mixture layer 10 and the surface of the positive electrode current collector 9 can be suppressed. have.

The negative electrode current collector 11 may be a metal such as aluminum, copper, nickel, stainless steel, an alloy thereof, or the like. Since the negative electrode current collector 11 is lightweight and has a high weight energy density, it is preferably aluminum and its alloy. The negative electrode current collector 11 is preferably copper in view of ease of processing into a thin film and cost.

The thickness of the negative electrode current collector 11 should just be 10 micrometers or more and 100 micrometers or less, Preferably it is 10 micrometers or more and 50 micrometers or less from a viewpoint of making the volume of the whole negative electrode small, and wound a negative electrode with a small curvature at the time of forming a battery. From a viewpoint to make it more preferable, they are 10 micrometers or more and 20 micrometers or less.

In one embodiment, the negative electrode mixture layer 12 contains a negative electrode active material and a binder.

As the negative electrode active material, those commonly used in the field of energy devices can be used. Specific examples of the negative electrode active material include metal lithium, lithium titanate (Li ₄ Ti ₅ O ₁₂ ), lithium alloys or other metal compounds, carbon materials, metal complexes, organic polymer compounds, and the like. The negative electrode active material may be one kind alone or a mixture of two or more kinds thereof. Examples of the carbon material include natural graphite (such as flaky graphite), graphite such as artificial graphite (graphite), amorphous carbon, carbon fiber and acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and the like. Can be mentioned. The negative electrode active material may be silicon, tin, or a compound containing these elements (oxides, nitrides, alloys with other metals) from the viewpoint of obtaining a larger theoretical capacity (for example, 500 to 1500 Ah / kg).

The average particle diameter (D ₅₀ ) of the negative electrode active material is preferably 1 μm or more, more preferably from the viewpoint of suppressing an increase in irreversible capacity accompanying a decrease in particle size, and achieving a good balance of a balance in which the electrolyte salt retention ability is improved. Is 5 µm or more, more preferably 10 µm or more, and preferably 50 µm or less, more preferably 40 µm or less, and still more preferably 30 µm or less. The average particle diameter (D ₅₀₎ of the negative electrode active material is measured by the same method as the average particle diameter (D ₅₀₎ of the above-described positive electrode active material.

Content of a negative electrode active material may be 60 mass% or more, 65 mass% or more, or 70 mass% or more based on the negative electrode mixture layer whole quantity. Content of a negative electrode active material may be 99 mass% or less, 95 mass% or less, or 90 mass% or less based on the negative electrode mixture layer whole quantity.

A binder and its content may be the same as the binder in the positive mix layer 10 mentioned above, and its content.

The negative electrode mixture layer 12 may further contain a conductive agent from the viewpoint of further lowering the resistance of the negative electrode 8. The electrically conductive agent and its content may be the same as the electrically conductive agent in the positive mix layer 10 mentioned above, and its content.

The negative electrode mixture layer 12 may further contain an ionic liquid.

As the ionic liquid, an ionic liquid used in an electrolyte composition described later can be used. The content of the ionic liquid contained in the negative electrode mixture layer 12 is preferably 3% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, based on the total amount of the negative electrode mixture layer. to be. The content of the ionic liquid contained in the negative electrode mixture layer 12 is preferably 30% by mass or less, more preferably 25% by mass or less, even more preferably 20% by mass or less based on the total amount of the negative electrode mixture layer. to be.

In the ionic liquid contained in the negative electrode mixture layer 12, the same electrolyte salt as that for the positive electrode mixture layer 10 described above may be dissolved.

The thickness of the negative mix layer 12 should just be 10 micrometers or more, 15 micrometers or more, or 20 micrometers or more. The thickness of the negative mix layer 12 should just be 100 micrometers or less, 80 micrometers or less, or 70 micrometers or less.

The electrolyte layer 7 is formed by, for example, fabricating an electrolyte sheet using an electrolyte composition. The electrolyte composition contains one or two or more polymers, oxide particles, at least one electrolyte salt selected from the group consisting of lithium salts, sodium salts, calcium salts and magnesium salts, and an ionic liquid.

The polymer preferably has a first structural unit selected from the group consisting of ethylene tetrafluoride and vinylidene fluoride.

The structural unit which comprises a polymer may contain the said 1st structural unit and the 2nd structural unit chosen from the group which consists of hexafluoropropylene, acrylic acid, maleic acid, ethyl methacrylate, and methyl methacrylate. That is, the 1st structural unit and the 2nd structural unit may be contained in 1 type of polymer, and may comprise the copolymer, It is contained in each other polymer, The 1st polymer which has a 1st structural unit, and a 2nd structural unit You may comprise at least 2 types of polymer of the 2nd polymer which has a.

Specifically, the polymer may be a copolymer of polyethylene ethylene, polyvinylidene fluoride, vinylidene fluoride and hexafluoropropylene.

The content of the polymer is preferably 3% by mass or more based on the total amount of the electrolyte composition (electrolyte layer). The content of the polymer is preferably 50% by mass or less, and more preferably 40% by mass or less based on the total amount of the electrolyte composition. The content of the polymer is preferably 3 to 50% by mass or 3 to 40% by mass based on the total amount of the electrolyte composition.

Since the polymer which concerns on this embodiment is excellent in affinity with the ionic liquid contained in electrolyte composition, the polymer in an ionic liquid is hold | maintained. This suppresses leakage of the ionic liquid when a load is added to the electrolyte composition.

The oxide particles may be, for example, particles of an inorganic oxide. The inorganic oxide may be, for example, an inorganic oxide containing Li, Mg, Al, Si, Ca, Ti, Zr, La, Na, K, Ba, Sr, V, Nb, B, Ge, and the like as constituent elements. The oxide particles are preferably at least one particle selected from the group consisting of SiO ₂ , Al ₂ O ₃ , AlOOH, MgO, CaO, ZrO ₂ , TiO ₂ , Li ₇ La ₃ Zr ₂ O ₁₂ and BaTiO ₃ . . Since the oxide particles have polarity, dissociation of the electrolyte in the electrolyte layer 7 can be promoted, thereby improving battery characteristics.

Oxide particles have a hydrophobic surface. Oxide particles usually have a hydroxyl group on the surface thereof and tend to exhibit hydrophilicity. In the oxide particles having a hydrophobic surface, the hydroxyl groups on the surface are reduced in comparison with the oxide particles having no hydrophobic surface. Therefore, the use of oxide particles having a hydrophobic surface, for the ionic liquid (for example, contained in the electrolyte composition, the anionic component is ^{_{N (SO 2 F) 2 -}} , N (SO 2 CF 3) 2 - ions having such Since the liquid) is hydrophobic, the affinity between these oxide particles and the ionic liquid is expected to be improved. Therefore, it is thought that the liquid holding property of the ionic liquid in the electrolyte layer is further improved, and as a result, the ionic conductivity is further improved.

The oxide particle which has a hydrophobic surface can be obtained by processing the oxide particle which shows hydrophilicity, for example with the surface treating agent which can give a hydrophobic surface. That is, the oxide particle which has a hydrophobic surface should just be the oxide particle surface-treated with the surface treating agent which can give a hydrophobic surface. As a surface treating agent, a silicon containing compound etc. are mentioned, for example.

The oxide particles having a hydrophobic surface may be oxide particles surface-treated with a silicon-containing compound. That is, the oxide particle which has a hydrophobic surface should just be what the silicon atom of the surface of an oxide particle and the silicon containing compound couple | bonded through the oxygen atom. The silicon-containing compound as the surface treating agent is preferably at least one selected from the group consisting of alkoxysilanes, epoxy group-containing silanes, amino group-containing silanes, (meth) acryloyl group-containing silanes, silazanes, and siloxanes.

Alkoxysilanes are methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethoxydiphenylsilane, n-propyltrimethoxysilane, hexyltrimethoxysilane, tetraethoxysilane , Methyl triethoxy silane, dimethyl diethoxy silane, n-propyl triethoxy silane and the like.

The epoxy group-containing silane is 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyl The diethoxysilane, 3-glycidoxypropyl triethoxysilane, etc. may be sufficient.

The amino group-containing silane is N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, N-2- (aminoethyl) -3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N What is necessary is just phenyl-3-aminopropyl trimethoxysilane.

The (meth) acryloyl group-containing silane is 3-methacryloyloxypropylmethyldimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane, 3- What is necessary is just methacryloyloxypropyl triethoxysilane, 3-acryloyloxypropyl trimethoxysilane, and the like. In addition, in this specification, a (meth) acryloyl group means acryloyl group or the methacryloyl group corresponding to this.

Silazane may be hexamethyldisilazane or the like.

The siloxane may be silicone oil such as dimethylsiloxane or the like. What is necessary is just to have a reactive functional group (for example, a carboxyl group) in these terminal or both terminal.

The oxide particle (surface-treated oxide particle) which has a hydrophobic surface may use what was manufactured by a well-known method, and may use a commercial item as it is.

Oxide particles are generally formed by aggregating primary particles (particles not constituting secondary particles) integrally forming a single particle and a plurality of primary particles as judged from the appearance geometry. It may contain tea particles.

The specific surface area of the oxide particles may be, for example, 2 to 380 m ² / g. If the specific surface area is 2 to 380 m ² / g, the secondary battery obtained tends to be excellent in discharge characteristics. From the same viewpoint, the specific surface area of the oxide particles may be 5 m ² / g or more, 10 m ² / g or more, 15 m ² / g or more, 20 m ² / g or more, or 30 m ² / g or more. Further, in view of ease of separation from the electrolyte layers described in the electrolyte sheet, having a specific surface area of the oxide particles is 350m ² / g or less, 300m ² / g or less, 250m ² / g or less, 200m ² / g or less, It may be 180 m ² / g or less, 150m ² / g or less, 130m ² / g or less, 100m ² / g or less, 80m ² / g or less, or 60m ² / g or less. The specific surface area of an oxide particle means the specific surface area of the whole oxide particle containing a primary particle and a secondary particle, and is measured by the BET method.

The average primary particle size of the oxide particles (average particle diameter of the primary particles) is preferably 0.005 μm (5 nm) or more, more preferably 0.01 μm (10 nm) or more, and even more preferably from the viewpoint of further improving the conductivity. It is 0.015 micrometer (15 nm) or more. The average primary particle diameter of the oxide particles is preferably 1 µm or less, more preferably 0.1 µm or less, still more preferably 0.05 µm or less from the viewpoint of making the electrolyte layer 7 thin. The average primary particle size of the oxide particles is preferably 0.005 to 1 µm, 0.01 to 0.1 µm, or 0.015 to 0.05 µm from the viewpoint of thinning the electrolyte composition and suppressing the protrusion of the oxide particles from the surface of the electrolyte composition. to be. The average primary particle size of the oxide particles can be measured by observing the oxide particles with a transmission electron microscope or the like.

The average particle diameter of the oxide particles is preferably 0.005 µm or more, more preferably 0.01 µm or more, and still more preferably 0.03 µm or more. The average particle diameter of the oxide particles is preferably 5 µm or less, more preferably 3 µm or less, still more preferably 1 µm or less. The average particle diameter of an oxide particle is measured by the laser diffraction method, and corresponds to the particle diameter which volume accumulation becomes 50%, when a volume cumulative particle size distribution curve is drawn from the small particle size side.

The shape of the oxide particles may be, for example, a block or substantially spherical shape. The aspect ratio of the oxide particles is preferably 10 or less, more preferably 5 or less, still more preferably 2 or less from the viewpoint of facilitating the thinning of the electrolyte layer 7. The aspect ratio is defined as the ratio of the length (maximum length of the particles) in the major axis direction of the particles and the length in the minor axis direction (minimum length of the particles) calculated from the scanning electron micrograph of the oxide particles. The length of a particle | grain is calculated | required statistically and calculates the said photograph using commercially available image processing software (for example, image analysis software by Asahi Kasei Engineering Co., Ltd., A phase group (registered trademark)).

The content of the oxide particles is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, particularly preferably 20 based on the total amount of the electrolyte composition (electrolyte layer). It is mass% or more, Preferably it is 60 mass% or less, More preferably, it is 50 mass% or less, More preferably, it is 40 mass% or less.

The electrolyte salt is at least one selected from the group consisting of lithium salts, sodium salts, calcium salts and magnesium salts. The electrolyte salt is a compound used to transfer cations between the positive electrode 6 and the negative electrode 8. The electrolyte salt is preferably low in dissociation at low temperatures, easy to diffuse in the ionic liquid, and not thermally decomposed by the high temperature, so that the environmental temperature at which the secondary battery can be used is widened. The electrolyte salt may be an electrolyte salt used in a fluorine ion battery.

Electrolyte salt anion component is halide ion ^{(I -, Cl -, Br} - , _{^{etc.), SCN -, BF 4 -}} , BF 3 (CF 3) -, BF 3 (C 2 F 5) -, PF 6 -, _{^{ClO 4 -, SbF 6 -,}} N (SO 2 F) 2 -, N (SO 2 CF 3) 2 -, N (SO 2 C 2 F 5) 2 -, B (C 6 H 5) 4 -, B _{(O 2 C 2 H 4)} 2 -, C (SO 2 F) 3 -, C (SO 2 CF 3) 3 -, CF 3 COO -, CF 3 SO 2 O -, C 6 F 5 SO 2 O - , B (O ₂ C ₂ O ₂ ) ₂ ^-and so on. Electrolyte salt anion moiety is preferably ^{_{N (SO 2 F) 2 -}} , N (SO 2 CF 3) 2 - anion of the formula (A) which are illustrated in the anion component of the ionic liquid, which will be described later, such component, PF _{^{6 -, BF 4 -, B}} (O 2 C 2 O 2) 2 - or ClO ₄ ^- is.

In addition, the following abbreviation may be used below.

^{[FSI] -: N (SO} 2 F) 2 -, bis (sulfonyl fluorophenyl) imide anion

^{[TFSI] -: N (SO} 2 CF 3) 2 -, bis (trifluoromethane sulfonyl) imide anion

^{[BOB] -: B (O} 2 C 2 O 2) 2 -, bis oxalate anion

^{[f3C] -: C (SO} 2 F) 3 -, tris (sulfonyl fluorophenyl) carbanion

Lithium salts are LiPF ₆ , LiBF ₄ , Li [FSI], Li [TFSI], Li [f3C], Li [BOB], LiClO ₄ , LiBF ₃ (CF ₃ ), LiBF ₃ (C ₂ F ₅ ), LiBF ₃ (C ₃ F ₇ ), LiBF ₃ (C ₄ F ₉ ), LiC (SO ₂ CF ₃ ) ₃ , CF ₃ SO ₂ OLi, CF ₃ COOLi and R'COOLi (R 'is an alkyl group having 1 to 4 carbon atoms, a phenyl group Or a naphthyl group).

Sodium salt is NaPF ₆ , NaBF ₄ , Na [FSI], Na [TFSI], Na [f3C], Na [BOB], NaClO ₄ , NaBF ₃ (CF ₃ ), NaBF ₃ (C ₂ F ₅ ), NaBF ₃ (C ₃ F ₇ ), NaBF ₃ (C ₄ F ₉ ), NaC (SO ₂ CF ₃ ) ₃ , CF ₃ SO ₂ ONa, CF ₃ COONa and R'COONa (R 'is an alkyl group having 1 to 4 carbon atoms, a phenyl group Or a naphthyl group).

Calcium salts include Ca (PF ₆ ) ₂ , Ca (BF ₄ ) ₂ , Ca [FSI] ₂ , Ca [TFSI] ₂ , Ca [f3C] ₂ , Ca [BOB] ₂ , Ca (ClO ₄ ) ₂ , Ca [ BF ₃ (CF ₃ )] ₂ , Ca [BF ₃ (C ₂ F ₅ )] ₂ , Ca [BF ₃ (C ₃ F ₇ )] ₂ , Ca [BF ₃ (C ₄ F ₉ )] ₂ , Ca [ C (SO ₂ CF ₃ ) ₃ ] ₂ , (CF ₃ SO ₂ O) ₂ Ca, (CF ₃ COO) ₂ Ca and (R'COO) ₂ Ca (R 'is an alkyl group having 1 to 4 carbon atoms, a phenyl group or a naph Or at least one selected from the group consisting of

Magnesium salts include Mg (PF ₆ ) ₂ , Mg (BF ₄ ) ₂ , Mg [FSI] ₂ , Mg [TFSI] ₂ , Mg [f3C] ₂ , Mg [BOB] ₂ , Na (ClO ₄ ) ₂ , Mg [ BF ₃ (CF ₃ )] ₂ , Mg [BF ₃ (C ₂ F ₅ )] ₂ , Mg [BF ₃ (C ₃ F ₇ )] ₂ , Mg [BF ₃ (C ₄ F ₉ )] ₂ , Mg [ C (SO ₂ CF ₃ ) ₃ ] ₂ , (CF ₃ SO ₃ ) ₂ Mg, (CF ₃ COO) ₂ Mg and (R'COO) ₂ Mg (R 'is an alkyl group having 1 to 4 carbon atoms, a phenyl group or a naphthyl group At least one selected from the group consisting of

The electrolyte salt is preferably one selected from the group consisting of imide lithium salts, imide sodium salts, imide calcium salts, and imide magnesium salts, and more preferably imide lithium salts.

The imide lithium salt may be Li [TFSI], Li [FSI], or the like. The imide sodium salt may be Na [TFSI], Na [FSI], or the like. The imide calcium salt may be Ca [TFSI] ₂ , Ca [FSI] ₂ , or the like. The imide magnesium salt may be Mg [TFSI] ₂ , Mg [FSI] ₂ , or the like.

The ionic liquid contains the following anionic components and cationic components. In addition, the ionic liquid in this embodiment is a substance which is a liquid at -20 degreeC or more.

Anion component of the ionic liquid is not particularly ^{limited, Cl -, Br -, I} - anions of halogens, such ^{_{as, BF 4 -, N (SO}} 2 F) 2 - inorganic anion, such _{as, B (C 6 H 5)} 4 _{^{-, CH 3 SO 2 O -}} , CF 3 SO 2 O -, N (SO 2 C 4 F 9) 2 -, N (SO 2 CF 3) 2 -, N (SO 2 C 2 F 5) 2 - , etc. Organic anion may be used.

The anion component of the ionic liquid preferably contains at least one kind of anion component represented by the following general formula (A).

N (SO ₂ C _m F _{2m + 1} ) (SO ₂ C _n F _{2n + 1} ) ^- (A)

m and n respectively independently represent the integer of 0-5. m and n may mutually be same or different, Preferably they are mutually the same.

Anion component represented by the formula (A) are, for example, _{N (SO 2 C 4 F 9} ) 2 -, N (SO 2 F) 2 -, N (SO 2 CF 3) 2 -, N (SO 2 C ₂ F _{5) 2} ^- is the rear surface.

Anion component of the ionic liquid is a relatively low-viscosity and in terms with further improved Sikkim The ion conductivity, which is also further improved charge-discharge characteristics, more _{preferably, N (SO 2 C 4 F} 9) 2 -, CF 3 SO ^{_{2 O -, N (SO 2}} F) 2 -, N (SO 2 CF 3) 2 - , and _{N (SO 2 C 2 F 5} ) 2 - containing at least one member selected from the group consisting of, and more preferably Contains N (SO ₂ F) ₂ ⁻ .

Although the cation component of an ionic liquid is not specifically limited, Preferably it is at least 1 sort (s) chosen from the group which consists of a linear quaternary onium cation, a piperidinium cation, a pyrrolidinium cation, a pyridinium cation, and an imidazolium cation.

Chain quaternary onium cation is a compound represented by following General formula (2), for example.

Equation (2):, R ¹ to R ⁴ each independently is a chain alkyl group having the carbon number of 1 to 20, or RO- (CH _{2) n} - chain alkoxyalkyl group (R is represented by methyl or ethyl, n Represents an integer of 1 to 4), and X represents a nitrogen atom or a phosphorus atom. Carbon number of the alkyl group represented by R <^1> -R <^4> becomes like this. Preferably it is 1-20, More preferably, it is 1-10, More preferably, it is 1-5.]

A piperidinium cation is a 6-membered ring cyclic compound containing nitrogen represented by following General formula (3), for example.

Equation (3) of, R ⁵ and R ⁶ are each independently a carbon number of 1 to 20 alkyl group, or RO- (CH _{2) n} - alkoxyalkyl group (R is represented by methyl or ethyl, n is 1 To an integer of 4 to 4). Carbon number of the alkyl group represented by R <^5> and R <^6> becomes like this. Preferably it is 1-20, More preferably, it is 1-10, More preferably, it is 1-5.]

A pyrrolidinium cation is a 5-membered ring cyclic compound represented, for example by following General formula (4).

[Equation (4) of, R ⁷ and R ⁸ are each independently a carbon number of 1 to 20 alkyl group, or RO- (CH _{2) n} - alkoxyalkyl group (R is represented by methyl or ethyl, n is 1 To an integer of 4 to 4). Carbon number of the alkyl group represented by R <^7> and R <^8> becomes like this. Preferably it is 1-20, More preferably, it is 1-10, More preferably, it is 1-5.]

A pyridinium cation is a compound represented, for example by General formula (5).

[Equation (5) of, R ⁹ to R ¹³ each independently represent a carbon number of 1 to 20 alkyl group, RO- (CH _{2) n} - alkoxyalkyl group (R is represented by methyl or ethyl, n is 1 to An integer of 4) or a hydrogen atom. Carbon number of the alkyl group represented by R <^9> -R <^13> becomes like this. Preferably it is 1-20, More preferably, it is 1-10, More preferably, it is 1-5.]

An imidazolium cation is a compound represented, for example by General formula (6).

[Formula (6) of, R ¹⁴ to R ¹⁸ each independently represent a carbon number of 1 to 20 alkyl group, RO- (CH _{2) n} - alkoxyalkyl group (R is represented by methyl or ethyl, n is 1 to An integer of 4) or a hydrogen atom. Carbon number of the alkyl group represented by R <^14> -R <^18> becomes like this. Preferably it is 1-20, More preferably, it is 1-10, More preferably, it is 1-5.]

The total content of the electrolyte salt and the ionic liquid (the ionic liquid in which the electrolyte salt is dissolved) may be 10% by mass or more based on the total amount of the electrolyte composition (electrolyte layer) from the viewpoint of appropriately producing the electrolyte layer, 80 mass% or less may be sufficient. The content of the ionic liquid is preferably 20% by mass or more, more preferably 30% by mass or more, based on the total amount of the electrolyte composition, from the viewpoint of enabling the lithium secondary battery to be charged and discharged at a high load rate.

The molar concentration of the ionic liquid in which the electrolyte salt is dissolved (the amount of the electrolyte salt per unit volume of the ionic liquid) is preferably 0.5 mol / L or more, more preferably 0.7 mol / L from the viewpoint of further improving the charge / discharge characteristics. More preferably, it is 1.0 mol / L or more, Preferably it is 2.0 mol / L or less, More preferably, it is 1.8 mol / L or less, More preferably, it is 1.6 mol / L or less.

The thickness of the electrolyte layer 7 is preferably 5 µm or more, and more preferably 10 µm or more, from the viewpoint of increasing the electrical conductivity and improving the strength. The thickness of the electrolyte layer 7 is preferably 200 µm or less, more preferably 150 µm or less, still more preferably 100 µm or less, particularly preferably 50 from the viewpoint of suppressing the resistance of the electrolyte layer 7. It is micrometer or less.

Subsequently, the manufacturing method of the secondary battery 1 mentioned above is demonstrated. The manufacturing method of the secondary battery 1 which concerns on this embodiment is the 1st process of forming the positive mix layer 10 on the positive electrode collector 9, and obtaining the positive electrode 6, and the negative electrode collector 11 phase. A second step of forming the negative electrode mixture layer 12 in the form of the negative electrode 8 and a third step of providing the electrolyte layer 7 between the positive electrode 6 and the negative electrode 8 are provided.

In the first step, the positive electrode 6 is, for example, dispersed in a dispersion medium using a kneader, a disperser, or the like to obtain a slurry-like positive electrode mixture, and then the positive electrode mixture is mixed with a doctor blade method, It is obtained by apply | coating on the positive electrode electrical power collector 9 by the dipping method, the spray method, etc., and volatilizing a dispersion medium after that. After volatilizing a dispersion medium, the compression molding process by a roll press may be provided as needed. The positive electrode mixture layer 10 may be formed as a positive electrode mixture layer having a multilayer structure by performing the steps from the application of the positive electrode mixture described above to volatilization of the dispersion medium a plurality of times.

The dispersion medium used in the first step may be water or 1-methyl-2-pyrrolidone (hereinafter also referred to as NMP). In addition, a dispersion medium is compounds other than the above-mentioned ionic liquid.

In the second step, the method of forming the negative electrode mixture layer 12 on the negative electrode current collector 11 may be the same method as the first step described above.

In the third step, in one embodiment, the electrolyte layer 7 is formed by producing an electrolyte sheet using the electrolyte composition. 4A is a schematic sectional view of an electrolyte sheet according to one embodiment. As shown in FIG. 4A, the electrolyte sheet 13A has a substrate 14 and an electrolyte layer 7 provided on the substrate 14.

The electrolyte sheet 13A is produced by, for example, dispersing a material used for the electrolyte layer 7 in a dispersion medium to obtain a slurry, and then applying this onto the substrate 14 to volatilize the dispersion medium. The dispersion medium is preferably water, NMP, toluene or the like.

The substrate 14 has heat resistance that can withstand the heating when the dispersion medium is volatilized. The substrate 14 is not limited as long as it does not react with the electrolyte composition and does not swell with the electrolyte composition, but may be formed of, for example, a resin. . The base material 14 should just be a film containing resin (general engineer plastics), such as a polyethylene terephthalate, a polytetrafluoroethylene, a polyimide, a polyether sulfone, and a polyether ketone.

The base material 14 should just have heat-resistant temperature which can endure the process temperature which volatilizes a dispersion medium in the process of manufacturing an electrolyte layer. The heat resistance temperature is a lower temperature in the softening point (temperature at which plastic deformation starts to deform) or the melting point of the substrate 14 when the substrate 14 is formed of a resin. The heat resistance temperature of the base material 14 is preferably 50 ° C or higher, more preferably 100 ° C or higher, even more preferably 150 ° C or higher, from the viewpoint of adaptability to the ionic liquid used for the electrolyte layer 7, For example, you may be 400 degrees C or less. If the base material which has the said heat resistance temperature is used, the above-mentioned dispersion medium (NMP, toluene, etc.) can be used suitably.

It is preferable that the thickness of the base material 14 is as thin as possible while maintaining the strength that can withstand the tensile force in the coating device. The thickness of the base material 14 is preferably 5 μm or more, more preferably 10 from the viewpoint of securing strength when applying the electrolyte composition to the base material 14 while reducing the volume of the entire electrolyte sheet 13A. 25 micrometers or more, More preferably, it is 25 micrometers or more, Preferably it is 100 micrometers or less, More preferably, it is 50 micrometers or less, More preferably, it is 40 micrometers or less.

The electrolyte sheet can also be produced continuously while winding in a roll. In that case, the electrolyte layer 7 may be damaged because the surface of the electrolyte layer 7 contacts the back surface of the substrate 14 and a part of the electrolyte layer 7 is attached to the substrate 14. In order to prevent such a situation, the electrolyte sheet may be provided with a protective material on the opposite side to the substrate 14 of the electrolyte layer 7 as another embodiment. 4B is a schematic sectional view showing an electrolyte sheet according to another embodiment. As shown in FIG. 4B, the electrolyte sheet 13B further includes a protective material 15 on the side opposite to the base material 14 of the electrolyte layer 7.

The protective material 15 should just be easily peelable from the electrolyte layer 7, Preferably it is nonpolar resin films, such as polyethylene, a polypropylene, and poly tetrafluoro ethylene. When the nonpolar resin film is used, the electrolyte layer 7 and the protective material 15 are not stuck to each other, and the protective material 15 can be easily peeled off.

The thickness of the protective material 15 is preferably 5 µm or more, more preferably 10 µm, further preferably 100 µm or less, from the viewpoint of securing strength while reducing the volume of the entire electrolyte sheet 13B. Preferably it is 50 micrometers or less, More preferably, it is 30 micrometers or less.

The heat resistant temperature of the protective material 15 is, from the viewpoint of suppressing deterioration in a low temperature environment and suppressing softening under a high temperature environment, preferably -30 ° C or more, more preferably 0 ° C or more, and further preferably It is 100 degrees C or less, More preferably, it is 50 degrees C or less. When providing the protective material 15, since the above-mentioned volatilization process of a dispersion medium is not essential, it is not necessary to make heat resistance temperature high.

In the method of providing the electrolyte layer 7 between the positive electrode 6 and the negative electrode 8 using the electrolyte sheet 13A, for example, the substrate 14 is peeled from the electrolyte sheet 13A, and the positive electrode 6 ), The secondary battery 1 is obtained by laminating the electrolyte layer 7 and the negative electrode 8 by lamination. At this time, the electrolyte layer 7 is positioned on the positive electrode mixture layer 10 side of the positive electrode 6 and on the negative electrode mixture layer 12 side of the negative electrode 8, that is, the positive electrode current collector 9 and the positive electrode mixture layer. (10), the electrolyte layer 7, the negative electrode mixture layer 12, and the negative electrode current collector 11 are laminated in this order.

In a 3rd process, in another embodiment, the electrolyte layer 7 knead | mixes the material used for the electrolyte layer 7, and the obtained kneaded material is sandwiched between resin sheets, such as polytetrafluoroethylene (PTFE), and a roll It is formed by pressing with a press or the like to produce an electrolyte sheet.

Second Embodiment

Next, the secondary battery according to the second embodiment will be described. FIG. 5: is a schematic cross section which shows one Embodiment of the electrode group in the secondary battery which concerns on 2nd Embodiment. As shown in FIG. 5, the difference between the secondary battery in the second embodiment and the secondary battery in the first embodiment is that the electrode group 2B includes the bipolar electrode 16. That is, the electrode group 2B includes the positive electrode 6, the first electrolyte layer 7, the bipolar electrode 16, the second electrolyte layer 7, and the negative electrode 8 in this order. .

The bipolar electrode 16 includes the bipolar electrode current collector 17, the positive electrode mixture layer 10 provided on the surface (positive electrode surface) on the negative electrode 8 side of the bipolar electrode current collector 17, and the bipolar electrode current collector 17. The negative electrode mixture layer 12 provided in the surface (negative electrode surface) of the positive electrode 6 side of the () is provided.

In the bipolar electrode current collector 17, the positive electrode surface may preferably be formed of a material having excellent oxidation resistance, or may be formed of aluminum, stainless steel, titanium, or the like. The negative electrode surface in the bipolar electrode current collector 17 using graphite or an alloy as the negative electrode active material may be formed of a material which does not form an alloy with lithium, and specifically, may be formed of stainless steel, nickel, iron, titanium, or the like. You may be. When using different types of metals for the positive electrode surface and the negative electrode surface, the bipolar electrode current collector 17 may be a clad material in which different types of metal foil are laminated. However, when using the negative electrode 8 which operates in the potential which does not form an alloy with lithium like lithium titanate, the above-mentioned limitation is removed and the negative electrode surface should just be the same material as the positive electrode electrical power collector 9. In that case, the bipolar electrode current collector 17 may be a single metal foil. The bipolar electrode current collector 17 as a single metal foil may be an aluminum perforated foil, an expanded metal, a foamed metal plate, or the like having a hole having a hole diameter of 0.1 to 10 mm. In addition to the above, the bipolar electrode current collector 17 may be formed of any material as long as it does not cause changes in dissolution, oxidation, or the like during use of the battery, and its shape, manufacturing method, and the like are not limited.

The thickness of the bipolar electrode current collector 17 should just be 10 micrometers or more and 100 micrometers or less, Preferably it is 10 micrometers or more and 50 micrometers or less from a viewpoint of making the volume of the whole positive electrode small, and when forming a battery, a bipolar electrode is small curvature. From a viewpoint of winding up, More preferably, they are 10 micrometers or more and 20 micrometers or less.

Next, the manufacturing method of the secondary battery which concerns on 2nd Embodiment is demonstrated. The secondary battery manufacturing method according to the present embodiment includes a first step of forming the positive electrode mixture layer 10 on the positive electrode current collector 9 to obtain the positive electrode 6, and the negative electrode mixture on the negative electrode current collector 11. In the second step of forming the layer 12 to obtain the negative electrode 8, the positive electrode mixture layer 10 is formed on one side of the bipolar electrode current collector 17, and the negative electrode mixture layer 12 is formed on the other side. A third step of forming the bipolar electrode 16 and a fourth step of providing the electrolyte layer 7 between the positive electrode 6 and the bipolar electrode 16 and between the negative electrode 8 and the bipolar electrode 16. Have

The 1st process and the 2nd process should just be a method similar to the 1st process and 2nd process in 1st Embodiment.

In the third step, the method of forming the positive electrode mixture layer 10 on one surface of the bipolar electrode current collector 17 may be the same method as the first step in the first embodiment. The method of forming the negative mix layer 12 on the other surface of the bipolar electrode collector 17 may be a method similar to the 2nd process in 1st Embodiment.

As a method of providing the electrolyte layer 7 between the positive electrode 6 and the bipolar electrode 16 during the fourth step, in one embodiment, the electrolyte layer 7 is formed by producing an electrolyte sheet using an electrolyte composition. do. The manufacturing method of the electrolyte sheet may be the same method as the manufacturing method of the electrolyte sheets 13A and 13B in the first embodiment.

In the fourth step, the method of providing the electrolyte layer 7 between the negative electrode 8 and the bipolar electrode 16 includes providing the electrolyte layer 7 between the positive electrode 6 and the bipolar electrode 16 described above. What is necessary is just the same method as the method.

Example

Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited to these Examples.

Example 1-1

<Production of Electrolyte Layer>

Lithium bis (trifluoromethanesulfonyl) imide (Li [TFSI]) dried under a dry argon atmosphere was used as an electrolyte salt, and an ionic liquid, N, N-diethyl-N-methyl-N- (2- The electrolyte salt was dissolved in methoxyethyl) ammonium bis (trifluoromethanesulfonyl) imide ([DEME] [TFSI]) at a concentration of 1.5 mol / L (hereinafter, the composition of the ionic liquid in which the electrolyte salt was dissolved When it shows, it may describe as "the density | concentration of electrolyte salt / the kind of electrolyte salt / the kind of ion liquid."). Subsequently, SiO ₂ particles “RX50” surface-treated with a copolymer of vinylidene fluoride and hexafluoropropylene as a polymer (PVDF-HFP) and silazane (hexamethyldisilazane) as oxide particles having a hydrophobic surface. : AEROSIL RX50, manufactured by Nippon Aerosil Co., Ltd., specific surface area: 35 m ² / g, average primary particle size: about 40 nm), followed by addition of N-methyl-2-pyrrolidone (NMP) as a dispersion medium. And the slurry was produced. The slurry of the electrolyte composition was obtained by further adding and mixing the ionic liquid (1.5 mol / L / Li [TFSI] / [DEME] [TFSI]) in which the electrolyte salt mentioned above was dissolved to this slurry. At this time, the mass ratio of the polymer, the oxide particles, and the ionic liquid in which the electrolyte salt was dissolved in the electrolyte composition was ionic liquid in which the polymer: oxide particle: electrolyte salt was dissolved = 34: 23: 43. Thereafter, NMP was further added to adjust the viscosity, and the slurry was applied using an applicator on a polyethylene terephthalate base material (product name: Theonex R-Q51, manufactured by Teijin DuPont Film Co., Ltd., 38 μm in thickness). It was. The slurry applied was volatilized by heating and drying at 80 degreeC for 1 hour, and the electrolyte sheet was obtained. The obtained electrolyte sheet was punched to φ 16 mm to obtain an electrolyte layer.

<Production of positive electrode>

78.5 parts by mass of layered lithium nickel manganese cobalt composite oxide (positive electrode active material), acetylene black (conductor, average particle diameter of 48 nm, product name: HS-100, Denka Co., Ltd.) 5 parts by mass, vinylidene fluoride and hexafluoro 2.5 mass parts of copolymer solutions (binder, 12 mass% of solid content) of propylene, and the ionic liquid (1.5 mol / L / Li [FSI] / [Py13] [FSI] (N-methyl-N) which melt | dissolved the electrolyte salt 14 parts by mass of -propylpyrrolidinium bis (fluorosulfonyl) imide))) was mixed to prepare a positive electrode mixture slurry. The positive electrode mixture slurry was coated on a current collector (aluminum foil having a thickness of 20 μm) with a coating amount of 147 g / m ² , and dried at 80 ° C. to form a positive electrode mixture layer having a mixture density of 2.9 g / cm ³ . This was punched to φ 15 mm to make a positive electrode.

<Production of negative electrode>

78 parts by mass of graphite 1 (negative electrode active material, manufactured by Hitachi Kasei Co., Ltd.), 2.4 parts by mass of graphite 2 (negative electrode active material, manufactured by Nippon Kokuen Kogyo Co., Ltd.), carbon fiber (conductive agent, product name: VGCF-H, Sho) 0.6 parts by mass of Denko Corporation, 5 parts by mass of a copolymer solution of vinylidene fluoride and hexafluoropropylene (a binder, 12 parts by mass of solids), and an ionic liquid (1.5 mol / L / Li) in which an electrolyte salt is dissolved [FSI] / [Py13] [FSI]) 14 parts by mass were mixed to prepare a negative electrode mixture slurry. The negative electrode mixture slurry was coated on a current collector (copper foil having a thickness of 10 μm) with a coating amount of 68 g / m ² , and dried at 80 ° C. to form a negative electrode mixture layer having a mixture density of 1.9 g / cm ³ . This was punched out to 16 mm and used as the negative electrode.

<Production of coin type battery for evaluation>

The coin type battery for evaluation was produced using the positive electrode, electrolyte layer, and negative electrode. The positive electrode, the electrolyte layer, and the negative electrode were stacked in this order and placed in a coin cell container of the CR2032 type, and then the top of the battery container was coked and sealed through an insulating gasket.

Example 1-2

In the preparation of the electrolyte layer, as the oxide particles having a hydrophobic surface, SiO ₂ particles "RY50" surface-treated with siloxane (dimethylsilicone oil) instead of the SiO ₂ particles used in Example 1-1 (product name: AEROSIL RY50, A coin-type battery was produced in the same manner as in Example 1-1, except that Nippon Aerosil Co., Ltd., specific surface area: 30 m ² / g, average primary particle size: about 40 nm) was used.

Example 1-3

In the preparation of the electrolyte layer, SiO ₂ particles “RM50” surface-treated with (meth) acryloyl group-containing silanes instead of the SiO ₂ particles used in Example 1-1 as oxide particles having a hydrophobic surface (product name: AEROSIL A coin-type battery was produced in the same manner as in Example 1-1, except for using RM50, manufactured by Nippon Aerosil, Ltd., specific surface area: 50 m ² / g, average primary particle size: about 40 nm.

Example 1-4

In the preparation of the electrolyte layer, 1.5 mol / L / Li [FSI] instead of 1.5 mol / L / Li [TFSI] / [DEME] [TFSI] used in Example 1-1 as an ionic liquid in which the electrolyte salt was dissolved. ] And [Py13] [FSI] except for using a coin-type battery in the same manner as in Example 1-1.

Example 1-5

In the preparation of the electrolyte layer, the mass ratio of the polymer, the oxide particles and the ionic liquid in which the electrolyte salt is dissolved in the electrolyte composition is changed to the ionic liquid in which the polymer: oxide particle: electrolyte salt is dissolved = 30: 20: 50. A coin-type battery was produced in the same manner as in Example 1-4 except for this.

Example 1-6

In the preparation of the electrolyte layer, SiO ₂ particles “RX200” surface-treated with silazane (hexamethyldisilazane) instead of the SiO ₂ particles used in Example 1-1 as oxide particles having a hydrophobic surface. A coin-type battery was produced in the same manner as in Example 1-1, except that AEROSIL RX200, manufactured by Nippon Aerosil, Ltd., and had a specific surface area of 140 m ² / g and an average primary particle size of about 12 nm).

Example 1-7

In the preparation of the electrolyte layer, the mass ratio of the polymer, the oxide particles and the ionic liquid in which the electrolyte salt is dissolved in the electrolyte composition is changed to the ionic liquid in which the polymer: oxide particle: electrolyte salt is dissolved = 30: 20: 50. A coin-type battery was produced in the same manner as in Example 1-6 except for this.

Comparative Example 1-1

In the preparation of the electrolyte layer, in place of the SiO ₂ particles used in Example 1-1, the surface-treated hydrophilic SiO ₂ particles "S5130" (product name: S5130, manufactured by SIGMA-ALDRICH, specific surface area: 395 m ² / g, average Primary particle diameter: about 7 nm) and the coin-type battery in the same manner as in Example 1-1, except that the mass ratio of the polymer, the oxide particles, and the ionic liquid in which the electrolyte salt was dissolved was changed to 22:22:56. Was produced.

<Evaluation of discharge characteristic>

The discharge capacity at 25 ° C of the obtained coin-type batteries of Examples 1-1 to 1-7 and Comparative Example 1-1 was subjected to the following charging / discharging conditions using a charge / discharge device (manufactured by Toyo Systems Co., Ltd.). It was measured on the basis of.

(1) After performing constant current constant voltage (CCCV) charging at the end voltage 4.2V and 0.05C, three cycles of constant current (CC) discharge were performed at 0.05C to the end voltage 2.7V, and discharge capacity was calculated | required. In addition, C means "current value (A) / battery capacity (Ah)."

(2) Subsequently, after performing constant current constant voltage (CCCV) charging at the end voltage 4.2V and 0.1C, the cycle which discharges the constant current (CC) from 0.5C to the end voltage 2.7V was performed 1 cycle, and the discharge capacity was calculated | required.

From the obtained discharge capacity, the discharge characteristic (%) was computed using the following formula. It can be said that the discharge characteristic is excellent, so that the value is large. "A" was evaluated for the case where the discharge characteristic was 90% or more, and "B" for the case where the discharge characteristic was less than 90%. The results are shown in Table 1.

Discharge capacity x100 obtained at the third cycle of the discharge capacity / (1) obtained at the discharge characteristic (%) = (2)

Example 2-1

<Preparation of SiO ₂ Particles Surface-treated with Phenyltriethoxysilane>

SiO ₂ particles surface-treated with phenyltriethoxysilane were produced by the wet method. Acetic acid aqueous solution adjusted to pH 4 and ethanol were mixed by mass ratio 9: 1, and the mixed solution was prepared. The surface-treated hydrophilic SiO ₂ particles used in Comparative Example 1-1 were added to the mixed solution, followed by stirring for 10 minutes. Subsequently, phenyltriethoxysilane (product name: KBE-103, manufactured by Shin-Etsu Chemical Co., Ltd.) was added so as to be 1 mass% with respect to the hydrophilic SiO ₂ particles, and further stirred for 10 minutes. The mixed solution was filtered under reduced pressure, and the obtained powder (solid) was dried and pulverized at 100 ° C to obtain SiO ₂ particles surface-treated with phenyltriethoxysilane. The specific surface area of the obtained SiO ₂ particles was 395 m ² / g, and the average primary particle diameter was about 7 nm.

<Production of Electrolyte Layer>

Li [TFSI] dried under a dry argon atmosphere was used as an electrolyte salt, and the electrolyte salt was dissolved in a concentration of 1.5 mol / L in [DEME] [TFSI] as an ionic liquid. The SiO ₂ particles surface-treated with the ionic liquid in which the obtained electrolyte salt was dissolved and the phenyltriethoxysilane prepared in the above-mentioned were 30 minutes in methanol at a volume ratio (ionic liquid in which the electrolyte salt was dissolved: SiO ₂ ) 80:20. The mixture was mixed with stirring. Then, it distilled at 60 degreeC using the evaporator. The mixture obtained by distillation and polytetrafluoroethylene were mixed by mass ratio (mixture: polytetrafluoroethylene) 95: 5, and it knead | mixed for 30 minutes or more using mortar, and the electrolyte composition was obtained. At this time, the mass ratio of the polymer, the oxide particles, and the ionic liquid in which the electrolyte salt was dissolved in the electrolyte composition was ionic liquid in which the polymer: oxide particle: electrolyte salt was dissolved = 5: 40: 55. The obtained electrolyte composition was sandwiched between two polytetrafluoroethylene (PTFE) sheets and pressed with a roll press to obtain an electrolyte sheet having a thickness of 50 µm. The electrolyte sheet was punched out to have a diameter of 16 mm to form an electrolyte layer.

<Production of Evaluation Coin-Type Battery and Evaluation of Discharge Characteristics>

Except using the obtained electrolyte layer, it carried out similarly to Example 1-1, the coin-type battery was produced, and the same evaluation as Example 1-1 was performed. The results are shown in Table 2.

Comparative Example 2-1

The preparation of the electrolyte layer was carried out except that the surface-treated hydrophilic SiO ₂ particles used in Comparative Example 1-1 were used instead of the SiO ₂ particles surface-treated with phenyltriethoxysilane used in Example 2-1. In the same manner as in Example 2-1, the coin-type battery of Comparative Example 2-1 was produced, and the same evaluation as in Example 1-1 was performed. The results are shown in Table 2.

As shown in Table 1, the secondary batteries using the electrolyte compositions of Examples 1-1 to 1-7 containing oxide particles having a hydrophobic surface were those of Comparative Example 1-1 containing oxide particles having no hydrophobic surface. The discharge characteristics were superior to those of the secondary battery using the electrolyte composition. In addition, as shown in Table 2, also in the contrast between Example 2-1 and Comparative Example 2-1, the secondary battery using the electrolyte composition of Example 2-1, the electrolyte composition of Comparative Example 2-1 It was excellent in discharge characteristics compared with the used secondary battery. From these, it was confirmed that the electrolyte composition of this invention can manufacture the secondary battery excellent in discharge characteristics.

One… Secondary battery, 6.. Positive electrode, 7.. Electrolyte layer, 8.. Negative electrode, 9.. Positive electrode current collector, 10.. Positive electrode mixture layer, 11. Negative electrode current collector, 12.. Negative electrode mixture layer, 13A, 13B... Electrolyte sheet, 14... materials.

Claims (10)

One or two or more polymers,
Oxide particles having a hydrophobic surface,
At least one electrolyte salt selected from the group consisting of lithium salts, sodium salts, calcium salts and magnesium salts,
Ionic liquid
An electrolyte composition containing. The electrolyte composition according to claim 1, wherein the oxide particles are surface treated with a silicon-containing compound. The electrolyte composition according to claim 2, wherein the silicon-containing compound is at least one selected from the group consisting of alkoxysilanes, epoxy group-containing silanes, amino group-containing silanes, (meth) acryloyl group-containing silanes, silazanes, and siloxanes. The oxide particle according to any one of claims 1 to 3, wherein the oxide particles are SiO ₂ , Al ₂ O ₃ , AlOOH, MgO, CaO, ZrO ₂ , TiO ₂ , Li ₇ La ₃ Zr ₂ O _12, and BaTiO _3. Electrolyte composition which is at least 1 sort (s) of particle | grains chosen from the group which consists of. The group according to any one of claims 1 to 4, wherein the ionic liquid comprises a chain quaternary onium cation, a piperidinium cation, a pyrrolidinium cation, a pyridinium cation, and an imidazolium cation as the cation component. An electrolyte composition containing at least one selected from. The electrolyte composition according to any one of claims 1 to 5, wherein the ionic liquid contains, as an anion component, at least one of anion components represented by the following general formula (A).
N (SO₂C_mF_{2m + 1}) (SO₂C_nF_{2n + 1})^- (A)
[m and n each independently represent an integer of 0 to 5] The electrolyte composition according to any one of claims 1 to 6, wherein the polymer has a first structural unit selected from the group consisting of ethylene tetrafluoride and vinylidene fluoride. The second structure according to claim 7, wherein, in the structural unit constituting the polymer, the first structural unit is selected from the group consisting of hexafluoropropylene, acrylic acid, maleic acid, ethyl methacrylate, and methyl methacrylate. An electrolyte composition comprising a unit. The electrolyte composition according to any one of claims 1 to 8, wherein the electrolyte salt is an imide lithium salt. Positive electrode,
Negative,
An electrolyte layer comprising the electrolyte composition according to any one of claims 1 to 9 provided between the positive electrode and the negative electrode.
Secondary battery having a.

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